linux-kernel - Re: [PATCH V1 0/4] GPIO based PCIe Hot-Plug support

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Date:   Mon, 3 Oct 2022 20:21:47 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Jonathan Derrick <jonathan.derrick@...ux.dev>,
        Vidya Sagar <vidyas@...dia.com>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     Lukas Wunner <lukas@...ner.de>, bhelgaas@...gle.com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        lpieralisi@...nel.org, kw@...ux.com, thierry.reding@...il.com,
        jonathanh@...dia.com, mani@...nel.org,
        Sergey.Semin@...kalelectronics.ru, jszhang@...nel.org,
        linux-pci@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        kthota@...dia.com, mmaddireddy@...dia.com, sagar.tv@...il.com,
        Marek Behún <kabel@...nel.org>
Subject: Re: [PATCH V1 0/4] GPIO based PCIe Hot-Plug support

On Monday 03 October 2022 13:09:49 Bjorn Helgaas wrote:
> On Sat, Oct 01, 2022 at 05:50:07PM -0600, Jonathan Derrick wrote:
> > On 10/1/2022 10:20 AM, Pali Rohár wrote:
> > ...
> 
> > > Would not it better to rather synthesise PCIe Slot Capabilities support
> > > in your PCIe Root Port device (e.g. via pci-bridge-emul.c) and then let
> > > existing PCI hotplug code to take care for hotplugging? Because it
> > > already implements all required stuff for re-scanning, registering and
> > > unregistering PCIe devices for Root Ports with Slot Capabilities. And I
> > > think that there is no need to have just another (GPIO based)
> > > implementation of PCI hotplug.
> >
> > I did that a few years ago (rejected), but can attest to the robustness of
> > the pcie hotplug code on non-hotplug slots.
> > https://lwn.net/Articles/811988/
> 
> I think the thread is here:
> https://lore.kernel.org/linux-pci/1581120007-5280-1-git-send-email-jonathan.derrick@intel.com/
> and I'm sorry that my response came across as "rejected".  I intended
> it as "this is good ideas and good work and we should keep going".
> 
> Bjorn

Nice! So we have consensus that this is a good idea. Anyway, if you need
help with designing something here, please let me know as I have good
understanding of all (just two) consumers of pci-bridge-emul.c driver.